1. Field of the Invention
The present invention relates to a photoresist composition and, more particularly, to a photoresist composition that includes a polymer having at least one monomer that includes an acrylate or methacrylate group and further includes at least one fluoroalcohol group.
2. Description of the Related Art
The fabrication of advanced logic and memory devices involves patterning features with minimum ground rules which are constantly shrinking. Features less than 100 nm in size are initially formed in a high resolution resist which is patternwise exposed using exposure tools with wavelengths below 200 nm such as 193 nm, 157 nm, and 13 nm (EUV). Subsequently, the resist serves as an etch mask as openings in the pattern are transferred into the substrate. Therefore, the resist must not only have a desirable optical density at the exposure wavelength, but also have sufficient etch resistance to enable successful transfer of the image from patterned resist to the underlying substrate and to prevent edge roughness and an unacceptable etch bias in the resulting substrate pattern. Furthermore, high resolution features with the desired profiles are only achieved when the resist has an appropriate dissolution behavior in the aqueous base developer employed in the patterning process. For positive tone resists, a high dissolution rate in exposed regions (Rmax) and a low dissolution rate in unexposed regions (Rmin) is needed. However, Rmin should not be too low in order to avoid a skin or so called T-top on the patterned resist. For negative tone resists, unexposed regions should have a high dissolution rate to avoid scumming while exposed regions are typically crosslinked easily with a negligible film loss in the developer.
A trend in the industry is to incorporate fluorine (as C—F bonds) in the polymer composition which is the largest component of the coated resist film. Current advanced resists are based on polymers of methacrylates, acrylates, cyclic olefins or copolymers thereof. A beneficial attribute of fluorinated polymers is their low optical density.
For example, U.S. Patent Application Publication No. 2003/0224283 by Allen et al. discloses a photoresist composition that includes a polymer having at least one acrylate or methacrylate monomer with a fluoroalcohol moiety.
Unfortunately, increasing the fluorine content in a resist film decreases its etch resistance. Additionally, the dissolution rate of a resist may be difficult to adjust to a desirable range because of the fluorine content. Low etch resistance for polymers containing commercially available methacrylate or acrylate units are still a major concern. Therefore, improved polymers for high resolution resists are needed which have an acceptable optical density and dissolution behavior as well as higher etch resistance compared to state of the art polymers comprised of fluoroalcohol moieties.